Hcci/Hybrid engine Ideas

[SterlingPower]

Hello all,
I'm new to this forum and am interested in engineering, but am not classically trained im afraid,

I have been studing a number of engines and have a number of questions on them, and what people would think of them and their practical use, thanks.

1, is HCCI compatible with the Miller cycle?
It seems that HCCI a lower temperature engine but both are a lean burn concept it seems?

2, A 6 stroke idea (Bruce Crower) with the injection of water into the cylinder after the exaust has left converting to steam, the 40% savings sound optomistic to be honest
Would this result in cooling the block and premature wear, or reduced output from steam?
sending steam to an adjacent cylinder and keeping combustion and steam seperate would just make mechanical losses?

3, utilsation of the exhaust, coolant and aftercooler heat as a way of creating steam to drive a steam piston connected to the crankshaft, (turbo steamer) works on lower capacity engines only?

3b, Utilsation of exhaust heat, coolant and aftercooler to sterling engine connected to the crank/or an electrical generator
would there be enough energy to make it work or not be affective at all?

What do people think of the scuderi air hybrid, would a steam or air injection proccess in the combustion process make a differnce in the 6 stroke procces mentioned above, - is interested in trying a split cycle model engine

Thanks

 

[BrianPetersen]

1. Any piston engine utilizing a traditional 4-stroke cycle is compatible with being a Miller/Atkinson cycle engine. BUT ... The higher the compression ratio is of the base engine, and the faster the combustion process is, the more energy gets utilized within the "standard" portion of the power stroke of the engine, so the less benefit remains to be utilized if it were to be converted to Atkinson/Miller operation. Keep in mind that the Atkinson cycle inherently means you need a larger nominal displacement engine for a given target power output. On a high compression engine with a very fast combustion process (of which HCCI is an example - if you can get it to work reliably) it may be a situation where the extra displacement and extra friction and heat losses and weight associated with larger pistons etc may not be worthwhile. For example, if you start off with a normal turbodiesel engine, you *need* some energy left over in the exhaust to drive the exhaust turbine of the turbocharger. I've yet to see a turbodiesel made into an Atkinson/Miller cycle engine. It could very well be a situation where you are better off at the end of the day to downsize the engine and use a normal compression/expansion cycle with a normal turbo, than it is to up-size the engine to use Atkinson/Miller but have difficulty on the turbocharger side of things. Diesel without benefit of turbo is big, heavy, and slow ... even nowadays.

2. Of course, squirting water into the cylinder would cool the cylinder and pistons. You can probably design around any wear-related implications that this may have. There are a whole lot of other issues associated with this, and I agree that the proposed 40% savings sounds waaaaayyyyy optimistic.

3. I'm not aware of any displacement-related why a bottoming Rankine cycle will or won't work on a big versus small engine. The economics, the extra complexity, etc might not make it worthwhile in a small engine application, but that's another matter. Keep in mind that a good many natural-gas-fired (i.e. internal combustion engine...) central power plants already use a Rankine ("steam") bottoming cycle. The size and weight of the necessary heat exchangers, and the inherent slowness of thermal response, make this more practical on a stationary power plant, utility power generation scale. The BMW Turbosteamer system used the steam expansion cycle to provide power for engine accessories, etc., so that the steam expansion cycle could be decoupled from the power output of the combustion engine, so the slowness of thermal response didn't matter so much.

Regarding the Scuderi split cycle engine, they're claiming to have an operational prototype engine. "Show me the money" is a phrase that has come to mind for a LONG time.

By the way, HCCI is difficult to get to work outside the laboratory, but there are a number of other combustion concepts that exploit much of the same benefits without going "all the way" to proper HCCI, but by not going "all the way" to HCCI, they actually have promise of working over a more practical wide range of speed and load on the engine and ambient air temperature, and cold starting, and all the other headaches associated with "proper" and "true" HCCI operation.

 

[MikeHalloran]

1. I dunno.
2. ISTR he reported corrosion as a major issue, but Google will bury you.
3.,3b. Adding "stuff" to an engine adds bulk and weight. Neither is an issue for a stationary engine. Both are huge issues for vehicle engines.



Mike Halloran
Pembroke Pines, FL, USA

 

[SterlingPower]

Ok I would like to add further questions based on further reaseaching, looking at 6 cycle engines with a air 5/6 stroke and compatibility with other technologies working with natural gas,

If Air were to be used instead of steam saving on water costs, surely this would act as an airbrake in an engine 6 stroke or other wise, (split cycle) rather than expanding and providing extra power, if it were compressed air, then there would be more energy expended there than could be usefully extracted unless it was like a hybrid engine like the scuderi which im not sure would work, interesting concept as it is though.

So a Turbocompound device, (part of a turbo connected to the shaft thgouh reduction gear) which could return up to 10% savings would seem a better alternative over organic rankine cycle and the air/steam idea, if the air idea doenst work?
the higher the effiecny of an engine the less eneggy that can be extracted thgouh a turbocomound, but I figure a reasonable amount can be extracted thgouh a sterling enging at any output, is this true?
im assuming there would be need for a bypass valve and not all gasses would be able to pass thgouh less it create a large backpressure reducing output *multiple sterling units?)
Im curiois why sterling enignes havnt found a use in this aplication however (25%) efficeny reached so far,
Are they temprature and velocity sensitive or is it one of economics?

I would assume they are not as/compatible with somthing like HCCI (low temprature engine) and/or a turbocompound which would take most of the high value temprature energy from the engine, (loses 5% in the gearing)?

turbo compounded rotary units seem to have a high velocity exhaust but again that is mostly consumed by the turbos im reasoning leaving some or little energy that could be extracted by a sterling engine?
also their consumtion and oil use are well known,

Camless valves by solenoids are another intesting idea but control of them would be rather a nightmare to implement electronicly and havnt been used because of assocated risks?

thanks

Sterling Power

 

[BrianPetersen]

Turbocompounding by using an exhaust turbine geared to the crankshaft is not a new idea - some large WWII aircraft piston engines (spark ignition) used it.

Stirling engines have historically been enormous, heavy, slow devices with dismally low power output relative to the size and weight. Heat exchange just happens too slowly for them to be useful.

If you get the internal combustion engine part of the system correct (high compression and fast combustion process, but with sufficient dilution so that peak temperature doesn't cause excess NOx emissions) then all the extra hang-on devices to extract little bits of extra power out of the exhaust become redundant and serve little purpose. The tricky bit is to do this without detonation if you want to use premixed air and fuel (traditional spark ignition), and soot/NOx if you want to squirt fuel in late in the compression stroke to avoid detonation (traditional diesel).

 

[MikeHalloran]

Well, I can attempt to answer your last question.
Microcontrollers make it relatively simple to control things like electric engine valves, since machinery moves so much slower than electrons. However, electric engine valves require substantial electrical energy to open, and unlike with mechanical cams, you don't get any of it back when the valve closes. They're also, so far, not capable of great speed, and nobody has demonstrated long-term durability.



Mike Halloran
Pembroke Pines, FL, USA

 

[SMOKEY44211]

I'll offer my opinion to your questions. HCCI can be used in conjugtion with Miller/ Atkins cycle. By nature of the combustion proccess the near instant release of energy requires all engine components be extremly robust compaired to traditional diesel compression ignition. Reciprocating and rotating parts end up being very heavy especially when scaled 3dimensionally for larger displacements. One of the positive points of such an engine is that there is no need for artificial aspiration as it is already difficult to fuel it enough to consume all the oxygen. When done correctly NOX is close to zero without the need for pre or after treatments.
Six stroke has some merrit. 40% fuel savings is unrealistic. All engines need to have a high expansion ratio in order raise thermodynamic efficiency. Savings on the order of 5-15% are possible.
Turbo steamer has merrit. However I think heat exchanger in place of the radiator feeding hot water to exhaust jacket with a single expander is a much better aproach.
I'm going to skip 3b and address Scuderi engine. My opinion is that it is a money washing machine. (largely government funded.) Of course the thing runs. Please note that they publish torque and power #'s but nothing on BSFC. In the event someone from the company or from a certain congressmans office should be reading this I'll bet one of my engines will eclipes the scuderi engine in fuel efficiency. ---------Phil

 

[MikeHalloran]

I am related to the Scuderi family, but not associated in any way with their business. ...which AFAIK comprises raising PRIVATE capital, and using it to develop and attempt to market the engine invented and patented by Carmelo Scuderi.

They have engaged SWRI to do the mechanical development and performance testing. SWRI also consumes prodigious amounts of government money, which may be a source of confusion about where Scuderi Group's money came from.


Mike Halloran
Pembroke Pines, FL, USA

 

[potteryshard]

I had thought of using what might be called a 4 1/2 cycle approach... An expansion-only cylinder placed between pairs of working cylinders would recieve the residual exhaust pressure and expand down closer to atmospheric pressure. It seems that this could reduce waste heat through exhaust and also reduce noise. The expansion cylinder would probably need either a bigger bore or longer stroke than the working cylinders, but would see much lower pressures and so could be of much lighter construction.

The expansion cylinder throw would have to be at 180 crankshaft degrees from both adjacent cylinders, and so would create interesting balance problems. It might be a way to help recover high turbocharging pressures.

Worth the extra cubic invested in the engine? Probably not, but as always, it's fun to think about what else could be done.

 

[SterlingPower]

The Turbocompounded radial engines were less effiecnt than modern engines and had no catalysts so the exaust speed was also faster, im not sure that a turbocompound would make as mych differnce on a modern engine, 10% maybe

Im sure some people have experience with jake brakes here,
to use air as a way on increasing the effiecny in a 6 stroke 5 in /6 out cycle without air, compressed air would be required otherwise it would act like an air brake and more fuel would be required to return it to normal speeds?

It seems this and/or a turbocompound is the only way to ensure feesable fuel savings atm,

Heres a link to a sterling power heat recovery, so it seems that its practical for industrial levels of heat, rather csotly at $1200-2000/kw however. I like the idea of a single expander on the exhuast thgouh

http://peswiki.com/index.php/Directory:ReGen_Power_Systems

again with a turbocompound on an 6 stroke air cycle it would be aditionally slowed down?

Thanks

 

[HRHtex]

SterlingP - turbocompounds and Crower-type arrangements are not the simplest way of increasing fuel efficiency.
There are big gains possible through reduction of SI engines' pumping losses. In an urban environment with a lot of stop/start and part-throttle driving this could be as high as maybe a 20% fuel saving. Reduction of pumping losses is probably best achieved by LIVC control. Unfortunately this requires control over a continuous very wide range of valve opening duration. The still-to-be-made-practical "camless" valve systems will be able to do this. The little known mechanical system, the "Helical Camshaft" can also achieve the necessary range of duration change.

Although interesting, proposed Stirling or steam power heat recovery systems are just not practical for automotive use on the grounds of simplicity.
About the only novel system that could be used is maybe a "blowdown" turbine on the exhaust driving an alternator and then an electric motor on the crankshaft. I imagine that this has probably been already thoroughly investigated by many car companies.

Which leads to another point - no matter what idea you can come up with, there is a 99% chance that it has already been thought of and thoroughly studied. (But that is not to say you should not keep trying to come up with something new).

 

[dgallup]

The simplest variable valve lift & duration system I have seen is the Fiat MultiAir system. I expect this approach to be very successful.

Electro magnetic camless systems are non starters.

 

[SomptingGuy]

Electro magnetic camless systems are are non starters for production intent. But they are pretty useful when starting with a blank sheet and investigating strategies.


- Steve

 

[HRHtex]

I agree that camless systems are non-starters at present but you never know what sudden developments may occur.

On the subject of the Helical Camshaft - a couple of years ago I worked for a company that sent me to see the cam demonstrated and to talk to the the people involved. I was very impressed with the demo. - just like that shown on the internet video. Any engine strategy that needs a continuous wide range of duration at full lift - this system can do it.
I never really found out why the company didn't get involved with the cam project - possibly internal company politics.
The Helical cam also relates to the topic of coming up with new ideas - it is a totally new idea - so apparently it is still possible to come up with new ideas for mechanical devices. I can't think any other genuinely new mechanical ideas in the automotive field.

 

[Lou Scannon]

I've said this before, in my book, any discussion of a novel heat engine that supposedly eclipses the state of the art should be accompanied by P-V and T-S diagrams.
Now, the diagrams may or may not be valid, but if not they will be readily de-bunked in due course.

...Next.